A Multisensor System for The Detection and Characterization of Uxo

A prototype active electromagnetic system has been developed for detecting and characterizing<br>UXO. The system employs two orthogonal vertical loop transmitters and a pair of horizontal loop<br>transmitters spaced apart vertically by 0.7 m. Eight vertical field detectors are deployed in the plane of<br>each of the horizontal loops and are arranged to measure offset vertical gradients of the fields. The<br>location and orientation of the three principal polarizabilities of a target can be recovered from a single<br>position of the transmitter-receiver system. Further characterization of the target is obtained from the<br>broadband response. The system employs a bipolar half sine pulse train current waveform and the<br>detectors are dB/dt induction coils designed to minimize the transient response of the primary field<br>pulse. The target transient is recovered in a 40 μsec to 1.0 msec window. The ground response imposes<br>an early time limit on the time window and system/ambient noise limits the late time response.<br>Nevertheless for practical transmitter moments and optimum receivers the size and the ratio of<br>conductivity to permeability can be accurately recovered. The prototype system has successfully<br>recovered the depths and polarizabilities of ellipsoidal test targets.